The present invention relates to a scroll fluid machine suitable for use in an air compressor, a vacuum pump, etc. by way of example.
In general, a scroll fluid machine has a casing and a fixed scroll member provided in the casing. A driving shaft is rotatably provided in the casing. An orbiting scroll member is orbitably provided on the distal end of the driving shaft in the casing to come in sliding contact with the fixed scroll member in the axial direction. A plurality of compression chambers are defined between the orbiting scroll member and the fixed scroll member [for example, see Japanese Patent Application Unexamined Publication (KOKAI) Nos. 6-26484 (1994) and 9-144674 (1997)].
In this type of conventional scroll fluid machine, the driving shaft is externally driven to rotate, causing the orbiting scroll member to perform an orbiting motion with a predetermined eccentricity with respect to the fixed scroll member, thereby sucking a fluid, e.g. air, from a suction opening provided at the outer periphery of the fixed scroll member, and successively compressing the fluid in the compression chambers formed between the wrap portions of the fixed and orbiting scroll members. Finally, the compressed fluid is discharged to the outside from a discharge opening provided in the center of the fixed scroll member.
Incidentally, in the above-described conventional scroll fluid machine, a crank shaft is provided at the distal end of the driving shaft at a position eccentric with respect to the axis of the driving shaft to orbitably support the orbiting scroll member at the distal end of the driving shaft. The crank shaft is integral with the driving shaft or provided as a member separate from the driving shaft.
Accordingly, the overall length of the driving shaft becomes extra longer by the length of the crank shaft. This causes the whole apparatus to increase in size in the axial direction unfavorably.
In view of the above-described problems with the prior art, an object of the present invention is to provide a scroll fluid machine designed to eliminate the need for a crank shaft for orbitably supporting an orbiting scroll member and to enable a reduction in overall length in the axial direction.